Diffuse light and galaxy interactions in the core of nearby clusters

TL;DR

This study uses planetary nebulae to analyze the kinematics of diffuse light in nearby galaxy clusters, revealing their dynamical states, formation histories, and comparing observations with Lambda-CDM simulations.

Contribution

It provides new insights into the dynamical status and formation processes of the intracluster light in galaxy clusters using planetary nebulae as probes.

Findings

Virgo and Coma cores are far from equilibrium with ongoing mergers.

Fornax and Hydra show accreted sub-components in their ICL.

Observed ICL properties qualitatively agree with Lambda-CDM simulations.

Abstract

The kinematics of the diffuse light in the densest regions of the nearby clusters can be unmasked using the planetary nebulae (PNs) as probes of the stellar motions. The position-velocity diagrams around the brightest cluster galaxies (BCGs) identify the relative contributions from the outer halos and the intracluster light (ICL), defined as the light radiated by the stars floating in the cluster potential. The kinematics of the ICL can then be used to asses the dynamical status of the nearby cluster cores and to infer their formation histories. The cores of the Virgo and Coma are observed to be far from equilibrium, with mergers currently on-going, while the ICL properties in the Fornax and Hydra clusters show the presence of sub-components being accreted in their cores, but superposed to an otherwise relaxed population of stars. Finally the comparison of the observed ICL properties with those predicted from Lambda-CDM simulations indicates a qualitative agreement and provides insights on the ICL formation. Both observations and simulations indicate that BCG halos and ICL are physically distinct components, with the ``hotter" ICL dominating at large radial distances from the BCGs halos as the latter become progressively fainter.